Kids' ski boots, and the shells that grow six sizes

Who each of these is for, and who should skip it

This is the whole decision, and it is not about the boot. It is about how many days a year the child will ski.

• Under about five days a season: rent, or buy the adjustable shell. A junior rental package is cheap and the shop re-sizes it every visit. Our rent-or-buy page on boots says rent harder here than anywhere else on the site, and for a child it says it louder.
• Five to ten days, ages 5-10: the Roces Idea Up. Published to cover up to six sizes across 19.0-22.0 mondo, so one purchase covers several winters of a foot that grows a size a year.
• Five to ten days, age 10 and over: the Roces Idea Free. Same published adjustment, one band up at 22.5-25.5 mondo. This is the band where a fitted boot becomes a three-figure purchase that lasts one season.
• More than ten days, or a child in lessons who is linking turns: the Rossignol Comp J4. A soft adjustable shell is genuinely holding back a child who can ski, and this is the only boot here with a published flex index.
• Skip all three if they are under five. At two to five the boot is not the deciding purchase - the mittens and the snack are.

What this page ranks on

Children’s ski boots are a category where makers publish less than they do for adults, so the number of comparable figures is small. These are the ones that exist.

• 1. Published size range, in mondopoint. Mondo is the length of the foot in centimeters and it is the only ski boot measurement that means anything. A boot published as a band - 19.0-22.0 - is telling you how many winters it covers. The kids’ ski boot size chart converts a measured foot into that number.
• 2. Whether the shell adjusts, and by how much. Roces publishes “up to 6 sizes” per shell. Nothing else in this category publishes an adjustment range at all.
• 3. Published flex index. One boot here publishes one. Flex is how hard the cuff resists a forward lean, and a number is the only way to compare two boots on it - what the flex number actually means.
• 4. Published sole standard. Alpine junior (ISO 5355) or GripWalk, because a boot that does not match the binding does not go on the ski. The compatibility check nobody mentions.

The three, compared

Read that table and the shape of the decision is obvious. The two Roces boots publish a range and no performance figure. The Rossignol publishes a performance figure and no range. There is no boot in this category that publishes both, and anyone who tells you otherwise is describing a boot that does not exist.

The picks

Roces Idea Up, 19.0-22.0 MP

The answer for most families with a primary-school-age skier. Roces publishes a patented 6-in-1 system that it states lets one shell grow up to six sizes, and publishes this shell as 19.0-22.0 MP, EU 30-35, for ages 5 to 10. The adjustment is published as covering length, width and cuff height rather than length alone, which matters because a child’s foot gets wider as well as longer.

Three construction details are published and all three are about keeping a five-year-old dry and willing: a self-positioning liner tongue, a self-settling shell wrap that Roces states wraps the shell to resist water getting in, and slow memory recovery foam in the liner padding. The buckles are published as micrometric in aluminum and polycarbonate, which is a real specification rather than “durable plastic”.

Honest cons. No flex index is published, so you cannot compare it with a fitted boot on stiffness - and an adjustable two-piece shell is softer and less precise than a fitted boot, which a child notices the week they start carving. It is heavier for the same reason. Roces publishes no warranty term and no US price. And polypropylene is a durable shell material, not a performance one.

Roces Idea Free, 22.5-25.5 MP

The same published argument one size band up, and arguably the band where it matters most. Roces publishes this shell as 22.5-25.5 MP, EU 35.5-40, for age 10 and over, again stated as covering up to six sizes. Same published polypropylene shell, same Lycra easy-entry liner system.

Why this band is the expensive one: between about ten and fourteen a foot arrives at nearly adult length, and a fitted boot at that size costs adult money while lasting a single season. The teen gear page covers the rest of that size cliff, and the growing-room page draws the line between items you buy big and items you never do - ski boots being the hardest “never” on the site, which is exactly why a published adjustment range is worth paying for here.

Honest cons. The missing flex index matters more at this age than at five, because a twelve-year-old who skis will out-ski an adjustable shell before they out-grow it. The buckle count is not published for this model. No warranty term, no US price. If the child is in a race program or skiing twenty days a year, this is the wrong boot and the Rossignol is the right one.

Rossignol Comp J4

The fitted boot, and the only one here with numbers you can argue about. Rossignol publishes flex 50 on a junior last it states addresses common problem fit areas, four MACRO buckles, a polyolefin shell chosen for lightness, and a published mondo range of 22.0 to 26.5 - ten half-sizes, covering the whole upper half of childhood.

It is also published as GripWalk compatible, which is the single most useful thing on this page for anyone buying boots and skis separately. GripWalk soles are rockered and grippier to walk in, and they need a binding that accepts them. Our page on sole standards explains why this is the check that ruins afternoons when it is skipped, and the bindings page covers the other half.

Honest cons, and they are why this carries the skip note. One size, no growing room - this is a boot you replace, not extend. Rossignol publishes no warranty term and no US price for it, and no weight, so you cannot compare how much boot a child is actually lifting. And the GripWalk soles are published as sold separately, which is a second purchase nobody mentions in the shop.

How to size one without a shop visit

A ski boot is sized on the length of the foot in centimeters, not on a shoe size, and this is the one measurement worth doing properly at the kitchen table.

• Measure heel to longest toe, standing, in the sock they will ski in. One thin ski sock. Never two, and never a thick one - a thick sock makes a foot colder, not warmer, and in a ski boot it also ruins the fit.
• Measure both feet and use the longer one. Then read the number straight off the kids’ ski boot size chart - a foot measuring 21.4 cm is a mondo 21.5, not a “size 2”.
• Do not add growing room to a fitted boot. A loose ski boot is not a minor nuisance like a loose snow boot; the foot slides, the child cannot steer, and the day ends early. This is the entire argument for an adjustable shell: it is the only honest way to buy growing room in a ski boot.
• With an adjustable shell, set it to the measured size and leave it. The point of the mechanism is that you move it next winter, not that you ski the whole range at once.
• Check the shell length before the first day. Toes should brush the front when standing upright and pull back when the child bends their knees. If they are crushed standing up, it is too small whatever the chart said.

Why an adjustable shell is softer, and why that is fine

Worth understanding before you spend the money, because the trade is real and nobody selling either boot explains it.

A fitted boot is one molded shell. An adjustable boot is two pieces that slide against each other, with a mechanism in between. Every mechanism is a place where force gets absorbed instead of transmitted, which is why an adjustable boot feels vaguer underfoot and why no maker publishes a flex index for one - the number would not mean the same thing.

For a child on a learning slope that vagueness is close to irrelevant. They are not loading the cuff hard enough to notice, and the boot that actually fits beats the boot that transmits well. The crossover comes when they can link turns on a blue run and are skiing enough days to want more from the equipment - which, for most families on this site, is a conversation for a later season than the one where they bought their first boots.

What the boots have to work with

Boots are one of two components that have to match each other, and the other one is the ski.

• Skis with bindings. Kids’ skis with bindings from 70 cm up - a junior system binding adjusts across a range of boot sole lengths, which is what makes a growing boot workable at all.
• The right ski length. The kids’ ski size chart, which is sized on height rather than on the boot.
• Socks, and only one pair. The best kids’ ski socks, and the rule parents get backward.
• Somewhere to dry them. A wet liner is a cold foot the next morning - boot dryers and the free condo method.